Air cleaners are widely used in home and office settings for cleaning the air. An air cleaner can filter the air in order to remove airborne contaminants. An air cleaner can therefore include any type of mechanical filter element comprising a mesh, a weave, a foam, etc.
In addition to filtering particles out of the air, an air cleaner can include an air ionizer (such as an electrostatic precipitator with a corona field or pre-ionizer element) that ionizes airflow passing through the air cleaner. The ionization transforms stable (O2) molecules in the air into ozone molecules (O3), where the ozone molecules are a by-product of the ionization process. Subsequently, the third oxygen atoms of the ozone molecules enter into destructive reactions with contaminants in the vicinity by oxidizing compounds they come into contact with. The oxidation can add oxygen molecules to these contacted compounds during the oxidation reaction.
Ozone is a powerful oxidizer because it is not a stable molecule. Ozone molecules spontaneously return to a stable, molecular state by releasing their third oxygen atoms. However, the spontaneous breakdown of ozone does not occur immediately, and substantial amounts of ozone can linger in the airstreams for some time.
One of the great advantages of ozone is that it is not selective in the reactions it initiates. It neutralizes; harmful volatile organic compounds (VOCs) by oxidizing them. Ozone destroys pathogens (microorganisms), either by reducing or destroying them or by cell lysing or oxidation. Another beneficial effect of ozone is that ozone treatment of the air can remove some troublesome odors.
However, the use of ozone for air cleaning has drawbacks. Being a highly unstable and reactive form of oxygen, the ozone also reacts with living matter. Moderate concentrations of ozone, such as levels above regulation limits (for example, limits suggested by Underwriters Laboratories Inc. (UL)), are known to cause headaches, nausea, and irritation of mucous membranes. Higher levels of ozone cause progressively more severe respiratory problems. As a result, ozone in higher concentrations can be troublesome to humans and animals. Consequently, ozone should desirably be removed from the air after generation.
Ozone removal filters are known. U.S. Pat. No. 6,375,905 to Moini et al. discloses an ozone removal filter that comprises an aluminum foil substrate that is impregnated with a catalyst. Air flows through the substrate, contacting the catalyst. The catalyst subsequently breaks down ozone in the airstream. The substrate of Moini comprises sandwiched sheets of aluminum foil. Each sheet receives a series of slits, with the sheet being subsequently stretched and twisted, wherein the slits are transformed into geometrically-shaped openings. Multiple such sheets are stacked together into a sandwich. The openings formed in one sheet do not align with the openings formed in adjacent sheets. Moini discloses that the airflow traveling through the substrate is forced to travel in a zig zag pattern (see FIGS. 6-7 and col. 8, lines 14-25). The assembled sandwich of multiple sheets can then be crimped or formed into a serpentine shape (see FIG. 8), allowing the final substrate to be shaped or formed.